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27.2.2 基本的定制控件
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C#高级编程（第3版）
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27.2.2 基本的定制控件
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2006-10-13 14:41:00
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<h1 id="divCurrentNode" style="color: #b83507; width: 100%; text-align: left; font-size: 12px; padding-left: 2px">当前章节:<a href='100165702.htm'><font color='red'>27.2.2 基本的定制控件</font></a></h1>
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<div style='float:left;width:49%'>·<a href='100165699.htm'>27.1 用户控件</a></div><div style='float:right;width:49%'>·<a href='100165700.htm'>27.2 定制控件</a></div><div style='float:left;width:49%'>·<a href='100165701.htm'>27.2.1 定制控件的项目配置</a></div><div style='float:right;width:49%'>·<a href='100165703.htm'>27.2.3 创建合成的定制控件</a></div><div style='float:left;width:49%'>·<a href='100165704.htm'>27.3 测验民意的投票控件</a></div><div style='float:right;width:49%'>·<a href='100165705.htm'>27.3.1 Candidate 控件</a></div></div>
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<link href="css.css" rel="stylesheet" type="text/css" /><h3 style='margin-top:8.15pt;margin-right:0cm;FTEL:8.15pt;margin-left:
0cm'><span lang=EN-US>27.2.2 </span><span style='font-family:黑体'>基本的定制控件</span></h3>
<p class=MsoNormal><span style='font-family:宋体'>从上一节的结果中可以推出，默认状态下生成的示例控件只是标准的</span><span
lang=EN-US><asp:Label></span><span style='font-family:宋体'>控件。项目</span><span
lang=EN-US>WebCustomControl1</span><span style='font-family:宋体'>的</span><span
lang=EN-US>.cs</span><span style='font-family:宋体'>文件中生成的代码如下</span><span
lang=EN-US>(</span><span style='font-family:宋体'>省略了标准和</span><span lang=EN-US>XML</span><span
style='font-family:宋体'>文档注释</span><span lang=EN-US>)</span><span
style='font-family:宋体'>：</span></p>
<p class=2 style='margin-top:8.15pt;margin-right:0cm;FTEL:0cm;
margin-left:21.45pt;FTEL:.0001pt;FTEL:18.45pt'><span
lang=EN-US>using System;</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt;line-height:13.5pt'><span
lang=EN-US>using System.Web.UI;</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt;line-height:13.5pt'><span
lang=EN-US>using System.Web.UI.WebControls;</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt;line-height:13.5pt'><span
lang=EN-US>using System.ComponentModel;</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt;line-height:13.5pt'><span
lang=EN-US> </span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt;line-height:13.5pt'><span
lang=EN-US>namespace PCSCustomWebControls</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt;line-height:13.5pt'><span
lang=EN-US>{</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt;line-height:13.5pt'><span
lang=EN-US> [DefaultProperty("Text"),</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt;line-height:13.5pt'><span
lang=EN-US> ToolboxData("<{0}:WebCustomControl1
runat=server><br>
</{0}:WebCustomControl1>")]</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt;line-height:13.5pt'><span
lang=EN-US> public class WebCustomControl1 :
System.Web.UI.WebControls.WebControl</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt;line-height:13.5pt'><span
lang=EN-US> {</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt;line-height:13.5pt'><span
lang=EN-US> private string text;</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt;line-height:13.5pt'><span
lang=EN-US> </span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt;line-height:13.5pt'><span
lang=EN-US> [Bindable(true),
Category("Appearance"), DefaultValue("")]</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt;line-height:13.5pt'><span
lang=EN-US> public string Text</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt;line-height:13.5pt'><span
lang=EN-US> {</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt;line-height:13.5pt'><span
lang=EN-US> get</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt;line-height:13.5pt'><span
lang=EN-US> {</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt;line-height:13.5pt'><span
lang=EN-US>
return text;</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt;line-height:13.5pt'><span
lang=EN-US> }</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt;line-height:13.5pt'><span
lang=EN-US> set</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt;line-height:13.5pt'><span
lang=EN-US> {</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt;line-height:13.5pt'><span
lang=EN-US>
text = value;</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt;line-height:13.5pt'><span
lang=EN-US> }</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt;line-height:13.5pt'><span
lang=EN-US> }</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt;line-height:13.5pt'><span
lang=EN-US> </span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt;line-height:13.5pt'><span
lang=EN-US> protected override void
Render(HtmlTextWriter output)</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt;line-height:13.5pt'><span
lang=EN-US> {</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt;line-height:13.5pt'><span
lang=EN-US> output.Write(Text);</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt;line-height:13.5pt'><span
lang=EN-US> }</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt;line-height:13.5pt'><span
lang=EN-US> }</span></p>
<p class=2 style='margin-top:0cm;margin-right:0cm;FTEL:8.15pt;
margin-left:21.45pt;FTEL:18.45pt'><span lang=EN-US>}</span></p>
<p class=MsoNormal><span style='font-family:宋体'>这里定义了一个类</span><span
lang=EN-US>WebCustomControl1(</span><span style='font-family:宋体'>注意类名是如何直接映射到前面示例中的</span><span
lang=EN-US>ASP.NET</span><span style='font-family:宋体'>元素上的</span><span
lang=EN-US>)</span><span style='font-family:宋体'>，它派生于前面讨论的</span><span
lang=EN-US>WebControl</span><span style='font-family:宋体'>类。这个类有两个属性：</span><span
lang=EN-US>DefaultProperty</span><span style='font-family:宋体'>和</span><span
lang=EN-US>ToolboxData</span><span style='font-family:宋体'>。属性</span><span
lang=EN-US>DefaultProperty</span><span style='font-family:宋体'>指定在支持此项功能的语言中使用时控件的默认特性。而属性</span><span
lang=EN-US>ToolboxData</span><span style='font-family:宋体'>指定在使用工具箱添加控件时添加给</span><span
lang=EN-US>.aspx</span><span style='font-family:宋体'>页面的</span><span lang=EN-US>HTML(</span><span
style='font-family:宋体'>如前所述，对项目进行编译后，配置工具箱，使用所创建的程序集，就可以把控件添加到工具箱上</span><span
lang=EN-US>)</span><span style='font-family:宋体'>。注意</span><span lang=EN-US>{0}</span><span
style='font-family:宋体'>占位符用于指定放置标记前缀的位置。</span></p>
<p class=MsoNormal><span style='font-family:宋体'>这个类包含属性</span><span lang=EN-US>Text</span><span
style='font-family:宋体'>。这是一个非常简单的文本属性，它与以前见到的文本属性非常类似。这里需要注意的是以下</span><span
lang=EN-US>3</span><span style='font-family:宋体'>个属性：</span></p>
<p class=1 style='margin-left:37.55pt;FTEL:-16.1pt'><span lang=EN-US>●<span
style='font:7.0pt "Times New Roman"'> </span></span><span
lang=EN-US>Bindable</span><span style='font-family:宋体'>：属性是否可以与数据绑定</span></p>
<p class=1 style='margin-left:37.55pt;FTEL:-16.1pt'><span lang=EN-US>●<span
style='font:7.0pt "Times New Roman"'> </span></span><span
lang=EN-US>Category</span><span style='font-family:宋体'>：在属性页面上的什么地方显示属性</span></p>
<p class=1 style='margin-left:37.55pt;FTEL:-16.1pt'><span lang=EN-US>●<span
style='font:7.0pt "Times New Roman"'> </span></span><span
lang=EN-US>DefaultValue</span><span style='font-family:宋体'>：属性的默认值</span></p>
<p class=MsoNormal><span style='font-family:宋体'>以这种方式给出属性与在定制控件中给出属性的方式相同，毫无疑问，这是给出公共字段的最佳方式。</span></p>
<p class=MsoNormal><span style='font-family:宋体'>类的其余部分是方法</span><span
lang=EN-US>Render()</span><span style='font-family:宋体'>。在设计定制的控件时，这是一个最重要的方法，因为它是访问输出流</span><span
lang=EN-US>(</span><span style='font-family:宋体'>目的是显示控件内容</span><span
lang=EN-US>)</span><span style='font-family:宋体'>的地方。但是以下两种情况不需要执行这个方法：</span></p>
<p class=1 style='margin-left:37.55pt;FTEL:-16.1pt'><span lang=EN-US>●<span
style='font:7.0pt "Times New Roman"'> </span></span><span
style='font-family:宋体'>设计的控件没有可视化的表示</span><span lang=EN-US>(</span><span
style='font-family:宋体'>通常称为组件</span><span lang=EN-US>)</span></p>
<p class=1 style='margin-left:37.55pt;FTEL:-16.1pt'><span lang=EN-US>●<span
style='font:7.0pt "Times New Roman"'> </span></span><span
style='font-family:宋体'>从现有的控件派生控件，并且不需要改变原有控件的显示特性</span></p>
<p class=MsoNormal><span style='font-family:宋体'>定制控件也可以有定制的方法、引发定制事件以及响应子控件</span><span
lang=EN-US>(</span><span style='font-family:宋体'>如果子控件存在的话</span><span
lang=EN-US>)</span><span style='font-family:宋体'>。在本章剩余的部分将介绍以下内容：</span></p>
<p class=1 style='margin-left:37.55pt;FTEL:-16.1pt'><span lang=EN-US>●<span
style='font:7.0pt "Times New Roman"'> </span></span><span
style='font-family:宋体'>创建派生的控件</span></p>
<p class=1 style='margin-left:37.55pt;FTEL:-16.1pt'><span lang=EN-US>●<span
style='font:7.0pt "Times New Roman"'> </span></span><span
style='font-family:宋体'>创建合成的控件</span></p>
<p class=1 style='margin-left:37.55pt;FTEL:-16.1pt'><span lang=EN-US>●<span
style='font:7.0pt "Times New Roman"'> </span></span><span
style='font-family:宋体'>创建更加高级的控件</span></p>
<p class=MsoNormal><span style='font-family:宋体'>最后一个示例是投票控件，它允许用户在几个投票选项中进行选择，并用图形显示投票的进程。其中的选项是使用嵌套的子控件定义的，定义的方式在前面描述过。</span></p>
<p class=MsoNormal><span style='font-family:宋体'>下面先创建一个简单的派生控件。</span></p>
<h4 style='FTEL:21.45pt'><span lang=EN-US>1.</span><span lang=EN-US
style='font-family:宋体'> </span><span lang=EN-US>RainbowLabel</span><span
style='font-family:黑体'>派生控件</span></h4>
<p class=MsoNormal><span style='font-family:宋体'>在第一个示例中，从</span><span
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